Multi-layered core golf ball

ABSTRACT

The present invention is directed towards a multi-layered core golf ball that comprises a center, a cover and at least two core layers formed around the center to create an inner ball, wherein the outermost core layer is relatively stiff and hard relative to the center. One outermost core layer is heavily filled with a density increasing material and at least one core layer functions as a moisture vapor barrier. One core layer may serve to provide all the functions in a single layer.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 10/002,641, filed Nov. 28, 2001, which is acontinuation-in-part of U.S. patent application Ser. No. 09/948,692,filed Sep. 10, 2001, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/172,608, filed Oct. 18, 1998, now U.S. Pat. No.6,302,808, which is a division of U.S. patent application Ser. No.08/943,932, filed Oct. 3, 1997, now U.S. Pat. No. 6,056,842, also acontinuation-in-part of U.S. application Ser. No. 08,996,718, filed Dec.23, 1997, now U.S. Pat. No. 6,124,389, which is a continuation-in-partof U.S. application Ser. No. 08/746,362, filed Nov. 8, 1996, now U.S.Pat. No 5,810,678, which is a continuation-in-part of U.S. patentapplication Ser. No. 08/706,008, filed Aug. 30, 1996, now U.S. Pat. No.5,813,923, which is a continuation-in-part of U.S. patent applicationSer. No. 08/603,057, filed Feb. 16, 1996, now U.S. Pat. No. 5,759,676,which is a continuation-in-part of U.S. patent application Ser. No.08/482,522, filed Jun. 7, 1995, now U.S. Pat. No. 5,688,191 also acontinuation-in-part of U.S. patent application Ser. No. 09/630,387,filed Aug. 1, 2000, which is a continuation-in-part of U.S. patentapplication Ser. No. 08/603,057, filed Feb. 16, 1996, now U.S. Pat. No.5,759,676; also the application is a continuation-in-part of U.S. patentapplication Ser. No. 09/815,753, filed Mar. 23, 2001, the disclosures ofwhich are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention is directed to improved golf balls and,specifically to golf balls comprised of one cover layer and amulti-layered core. More particularly, to where one of the outer corelayers is rigid and one of the inner core layers is flexible.

[0003] Generally, golf balls have been classified as wound balls orsolid balls. Wound balls are generally constructed from a liquid orsolid center surrounded by tensioned elastomeric material. Wound ballsare generally thought of as performance golf balls and have a goodresiliency, spin characteristics and feel when struck by a golf club.However, wound balls are generally difficult to manufacture whencompared to solid golf balls.

[0004] Early solid golf balls were generally two piece balls, i.e.,comprising a core and a cover. More recently developed solid balls arecomprised of a core, a mantle layer and a cover, in order to improve theplaying characteristics of the ball.

[0005] The prior art is comprised of a variety of golf balls that havebeen designed to provide particular playing characteristics. Thesecharacteristics are generally the initial velocity and spin of the golfball, which can be optimized for various types of players. For instance,certain players prefer a ball that has a high spin rate in order tocontrol and stop the golf ball. Other players prefer a ball that has alow spin rate and high resiliency to maximize distance. Generally, agolf ball having a hard core and a soft cover will have a high spinrate. Conversely, a golf ball having a hard cover and a soft core willhave a low spin rate. Golf balls having a hard core and a hard covergenerally have very high resiliency for distance, but are hard feelingand difficult to control around the greens. Various prior art referenceshave been directed to adding a mantle layer or second cover layer toimprove the playability of solid golf balls.

[0006] The spin rate of golf balls is the end result of many variables,one of which is the distribution of the density or specific gravitywithin the ball. Spin rate is an important characteristic of golf ballsfor both skilled and recreational golfers. High spin rate allows themore skilled players, such as PGA professionals and low handicappedplayers, to maximize control of the golf ball. A high spin rate golfball is advantageous for an approach shot to the green. The ability toproduce and control backspin to stop the ball on the green and side spinto draw or fade the ball substantially improves the player's controlover the ball. Hence, the more skilled players generally prefer a golfball that exhibits high spin rate.

[0007] On the other hand, recreational players who cannot intentionallycontrol the spin of the ball generally do not prefer a high spin rategolf ball. For these players, slicing and hooking are the more immediateobstacles. When a club head strikes a ball, an unintentional side spinis often imparted to the ball, which sends the ball off its intendedcourse. The side spin reduces the player's control over the ball, aswell as the distance the ball will travel. A golf ball that spins lesstends not to drift off-line erratically if the shot is not hit squarelyoff the club face. The low spin ball will not cure the hook or theslice, but the lower spin will reduce the adverse effects of the sidespin. Hence, recreational players prefer a golf ball that exhibits lowspin rate.

[0008] Reallocating the density or specific gravity of the variouslayers or mantles in the ball is an important means of controlling thespin rate of golf balls. In some instances, the weight from the outerportions of the ball is redistributed to the center of the ball todecrease the moment of inertia thereby increasing the spin rate. Forexample, U.S. Pat. No. 4,625,964 discloses a golf ball with a reducedmoment of inertia having a core with specific gravity of at least 1.50and a diameter of less than 32 mm and an intermediate layer of lowerspecific gravity between the core and the cover. U.S. Pat. No. 5,104,126discloses a ball with a dense inner core having a specific gravity of atleast 1.25 encapsulated by a lower density syntactic foam composition.U.S. Pat. No. 5,048,838 discloses another golf ball with a dense innercore having a diameter in the range of 15-25 mm with a specific gravityof 1.2 to 4.0 and an outer layer with a specific gravity of 0.1 to 3.0less than the specific gravity of the inner core. U.S. Pat. No.5,482,285 discloses another golf ball with reduced moment of inertia byreducing the specific gravity of an outer core to 0.2 to 1.0.

[0009] In other instances, the weight from the inner portion of the ballis redistributed outward to increase the moment of inertia therebydecreasing the spin rate. U.S. Pat. No. 6,120,393 discloses a golf ballwith a hollow inner core with one or more resilient outer layers,thereby giving the ball a soft core, and a hard cover. U.S. Pat. No.6,142,887 discloses an increased moment of inertia golf ball comprisingone or more mantle layers made from metals, ceramic or compositematerials, and a polymeric spherical substrate disposed inwardly fromthe mantle layers.

[0010] These and other references disclose specific examples of high andlow spin rate ball with ranges of specific gravity, ranges of diameterfor the core and ranges of thickness for the outer layers, etc. They,however, do not offer any universal guidelines to control the spin rateof golf balls. Hence, there remains a need in the art for an improvedgolf ball with controlled spin rates.

[0011] Other prior art golf balls have multiple core layers to providedesired playing characteristics. For example, U.S. Pat. No. 5,184,828claims to provide a golf ball having two core layers configured toprovide superior rebound characteristics and carry distance, whilemaintaining adequate spin rate. More particularly, the patent teaches aninner core and an outer layer and controlling the hardness distributionin the outer layer and in the inner core in such a way that the golfball has a maximum hardness at the outer site of the inner core. Thepatent alleges that such a distribution of hardness in the core assemblyallows high energy to accumulate at the interface region where thehardness is at a maximum. The patent further claims that the energy ofthe club face is efficiently delivered to the maximum hardness regionand transferred toward the inner core, resulting in a high reboundcoefficient. However, since golf balls having hard cores and soft coversprovide the most spin, the distribution taught by this patent wouldresult in maximum core hardness at the interface when hit by a driver.Therein the ball has a relatively high driver spin rate and not verygood distance. Since the ball in this patent has a softer outer corelayer, the ball should have a lower spin rate for shorter shots such asan eight iron, where spin is more desirable. Thus, the ball taught bythis patent appears to have many disadvantages.

[0012] In order to improve the playing characteristics of a solid golfball, Kasco, Inc. provided a ball called Rockets™. The Rockets™ ball iscomprised of a center, two layers and a cover. The center and the twolayers are all comprised of polybutadiene rubbers.

[0013] In particular, tests on such balls have shown that golf balls arecomprised of a center having a diameter of about 1.0 inch, a first layerhaving an average thickness of about 0.125 inch and a second layerhaving an average thickness of about 0.13 inch. The center has a Shore Chardness of about 59 at the center and 60 at the center mid pointbetween the core center and the outer surface of the center. The firstlayer has a Shore C hardness of about 61, and the second layer has aShore C hardness of about 73. The cover of the Rockets™ golf balls areharder than 65 Shore D and the compression is about 88.

[0014] Based upon the parting lines at each layer, it appears that Kascomanufactures the Rockets™ golf ball core by forming the center,compression molding the first layer around the center and compressionmolding the second layer onto the center and first layer. It appearsthat the cover is molded using a retractable pin injection mold. Theproblem with the Kasco method is that the golf balls thus formed havenon-concentric cores. That is, the center of the ball is not concentricwith the remainder of the ball and the layers do not have uniformthickness. More particularly, the first layer was measured to have amaximum thickness on one side of 0.139 inch and a minimum thickness onthe opposing side of 0.106 inch. Thus, there was a variance of 0.033inch in the thickness of the first layer. Similarly, the second layerwas measured to have a maximum thickness of 0.155 on a first side and aminimum thickness of 0.113 inch on the opposing side. Therefore, therewas a difference of 0.042 inch in the thickness of the second layer.Thus it is evident that there is a significant concentricity problem inthese golf balls.

SUMMARY OF THE INVENTION

[0015] The present invention is directed to an improved golf ball havinga core comprised of a center and multiple core layers to improve theplaying characteristics of the golf ball. More particularly, theinvention comprises a golf ball having a core and a cover in which thecore is comprised of a center and at least one core layer and preferablymulti-core layers surrounding the center. The center is preferablycomprised of a thermoset composition such as high cis or transpolybutadiene or may comprise a thermoset or thermoplastic metallocenesuch as polybutadiene, polyethylene copolymer. The core layers maycomprise the same materials as the center or different compositions.

[0016] At least one core layer should be significantly stiffer andharder than the innermost core. At least one layer has a Shore Chardness of greater than 80 and preferably greater than 90 with a flexmodulus of greater than about 30,000 psi and preferably, greater than40,000 psi. The flex modulus of each core layer covering the centerbecomes progressively larger as the layer moves away from the center.

[0017] At least one outermost core layer has a specific gravity ofgreater than 1.25 g/cc, preferably greater than 1.50 g/cc, and mostpreferably greater than 1.75 g/cc therein increasing the moment ofinertia of the overall golf ball and thereby lowering the spin rates.This outermost core layer may be heavily filled with density increasingmaterial while the center and any intermediate core layers may be filledwith a density reducing material, preferably greater than 2 g/cc, morepreferably greater than 5 g/cc and most preferably greater than 10 g/cc.

[0018] Optionally, one or more core layers, most preferably theoutermost core layer, serve as moisture barrier layers to reduce thepenetration of moisture into the center, which reduces COR values overtime.

[0019] The invention provides for a single core layer to serve all theabove functions: stiffness greater than the center; high specificgravity away from the center; and a barrier to penetrating moisture.

[0020] The cover comprises one or more layers of soft material thatsupplies high partial wedge spin and good durability. This material canbe a cast or reaction-injection molded polyurethane, polyurea,polyurethane-ionomer or a thermoplastic such as a thermoplasticurethane, partially or fully neutralized ionomer, metallocene or othersingle site catalyzed polymer, or blends thereof. The cover willpreferably have a Shore D hardness of less than 65 and a thickness offrom about 0.010 to 0.100 inches, more preferably from 0.020 to 0.040inches. Preferably, the cover comprises a single layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a cross-sectional view of a golf ball formed accordingto the present invention having two outer core layers.

[0022]FIG. 2 is a cross-sectional view of a golf ball formed accordingto the present invention showing five outer core layers.

[0023]FIG. 3 is a perspective view of a laminate comprising three layersof core material.

[0024]FIG. 4 is a sectional view of rollers and material being formedinto the laminate of core material.

[0025]FIG. 5 is a sectional view of a mold for forming multiple layersabout a core center according to the present invention.

[0026]FIG. 6 is a sectional view of a mold forming multiple layers abouta core center according to the invention with the mold-forming sheetsbeing vacuum formed within the mold.

[0027]FIG. 7 is a perspective view of a half mold used in formingmultiple layers about core centers in accordance with the presentinvention.

[0028]FIG. 8 is a cross-sectional view of a compression mold of a golfball core according to the present invention.

[0029]FIG. 9 is an exploded view of a golf ball core according to thepresent invention in a retractable-pin injection mold.

[0030]FIG. 10 is a cross-sectional view of a golf ball core according tothe present invention in a retractable-pin injection mold.

[0031]FIG. 11 is a cross-sectional view of a golf ball according to thepresent invention in a retractable-pin mold.

[0032]FIG. 12 is an exploded view of a golf ball core according to thepresent invention with cover layer hemispheres in a compression mold.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Referring to FIGS. 1 and 2, golf ball 10 includes a core 16 and acover 15. Core 16 includes a center 11, and at least one core layer.FIG. 1 depicts an embodiment of the invention having two outer corelayers, an intermediate core layer 13 and a relatively rigid outermostcore layer 14. However, FIG. 2 describes an embodiment having five corelayers. They are: a first intermediate core layer 17 a, a secondintermediate core layer 17 b, a third intermediate core layer 17 c, afourth intermediate core layer 17 d, and a fifth core layer which isgenerally very rigid, also referred to as the outermost core layer 14.

[0034] Referring to FIG. 2, the center 11 is preferably formed bycompression molding a sphere from a prep of center material. Compressionmolding solid centers is well known in the art.

[0035] Referring to FIGS. 3 and 4, in order to form multiple layersaround the center in a first embodiment of the invention, preferably alaminate 20 is formed. The laminate 20 is comprised of at least twolayers and preferably three layers 22, 23 and 24. The laminate 20 isformed from the rolling of thin sheets 32, 33, and 34 from a corematerial. More particularly, each sheet is formed to a thickness that isslightly larger than the thickness of the layers 12, 13 and 14 in thefinished golf ball 10. The thickness of each may be varied, but all havea thickness preferably of about 0.010 to about 0.100 inches and morepreferably from about 0.015 to 0.050 inches thick.

[0036] Preferably, the sheets 32, 33, 34 are prepared by mixing theuncured core material to be used for each layer and calendar rolling thematerial into sheets. The sheets are stacked together to form thelaminate 20 having three layers 22, 23 and 24 using calendar rollingmills. The sheets could also be made by extrusion. The sheets 32, 33 and34 should have very uniform thickness i.e. the thickness of each sheetshould not vary more than about 0.005 inch.

[0037] In an alternate embodiment, the laminate 20 can be furtherconstructed using an adhesive between each layer of material.Preferably, an epoxy resin such as Epoxy Resin #1028 from RBC Industriesin Warwick, R.I. is used. The adhesive should have good shear andtensile strength and, preferably the adhesive should have a tensilestrength over about 1500 psi. Still further, the adhesive should notbecome brittle when cured. An adhesive having a Shore D hardness of lessthan 60 when cured is preferred. The adhesive layer applied to thesheets should be very thin and preferably, less than about 0.004 inchthick.

[0038] Referring to FIGS. 5 through 8, the next step in the method ofthe present invention is to form multiple layers around the center. Thisis preferably accomplished by placing the two laminates 20 and 21 inbetween a top mold 36 and a bottom mold 37. The molds 36 and 37 arecomprised of mold frames 38 and replaceable mold halves 39 such as thatdescribed in U.S. Pat. No. 4,508,309 issued to Brown. The laminates 20and 21 are formed to the cavities in the mold halves 39. Preferably, thelaminates are suction formed by using a vacuum source 40. The vacuumsource 40 suction forms the laminates 20 and 21 to the half moldcavities 39 so that uniformity in layer thickness is maintained. Centers11 are inserted between the laminates after the laminates 20 and 21 havebeen formed to the cavities and the laminates 20 and 21 are compressionmolded about the centers 11 under conditions of temperature and,pressure that are well known in the art.

[0039] Referring to FIGS. 7 and 8, the half molds 39 have a plurality ofvents 41. The compression molding step includes flowing excess layermaterial from the laminates 20 and 21 through at least three vents 41 sothat the flow of laminate material is symmetrical about the center 11and the center 11 does not shift due to lateral flow patterns.Preferably, the half molds 39 have 4 to 6 vents.

[0040] Referring to FIGS. 9 through 12, the next step in the presentinvention is to form a cover 15 around the core 16. The core 16,comprised of center 11 and outer layers 12, 13 and 14, is supportedwithin a pair of cover mold-halves 50 and 51 by a plurality ofretractable pins 52. The retractable pins 52 are actuated byconventional means well known to those of ordinary skill in the art ofmold design.

[0041] After the mold-halves 50 and 51 are closed together with the pins52 supporting the core 16, the cover material is injected into the moldin a liquid state through a plurality of injection ports or gates 49.Gates 49 can be edge gates or sub-gates. With edge gates, the resultantgolf balls are all interconnected and may be removed from themold-halves 50 and 51 together in a large matrix. Sub-gatingautomatically separates the mold runner from the golf balls during theejection of the golf balls from mold-halves 50 and 51.

[0042] Referring to FIGS. 10 and 11, retractable pins 52 are retractedafter a predetermined amount of cover material has been injected intothe mold-halves 50 and 51. The predetermined amount of cover material issubstantially all of the material to be injected. Thus, the core 16 issubstantially surrounded by cover material and does not shift when theretractable pins 52 are removed. This allows the liquid cover materialto flow and substantially fill the cavity between the core 16 and themold-halves 50 and 51. At the same time, concentricity is maintainedbetween the core 16 and the mold-halves 50 and 51.

[0043] The cover material is allowed to solidify around the core 16,thereby forming cover 15. Golf ball 10 is then ejected from mold-halves50 and 51, and finished using processes which are well known in the art.The temperatures and curing time for mold-halves 50 and 51 are generallyknown in the art and are dependent on the material that is being usedfor cover 15, which will be discussed in more detail below.

[0044] Referring to FIG. 12, an alternative method of forming the cover15 according to the invention is shown. Two cover layer hemispheres 55and 56 are pre-formed of the desired cover material, preferably, by aninjection molding process. The hemispheres 55 and 56 are positionedaround core 16 thereby forming an assembly 57 that is then placed into acompression mold 58, which comprises two compression mold-halves 53 and54. Mold-halves 53 and 54 are advanced toward each other until theirmating surfaces touch, and the mold 58 is heated to melt thehemispheres. Mold-halves 53 and 54 compress and heat the hemispheres 55and 56 about the core 16 to mold the cover material thereto.

[0045] Referring back to FIGS. 1-2, the overall diameter of the core 16is greater than about 1.50 inches, preferably greater than 1.58 inchesand most preferably greater than about 1.60 inches. The center 11 has aShore C surface hardness of less than about 80, preferably less thanabout 70. The center 11 has a compression of less than about 70,preferably less than about 60 and most preferably less than about 50,and additionally has a COR value greater than about 0.700 and preferablygreater than about 0.750. Compression is measured by applying aspring-loaded force to the golf ball center, golf ball core or the golfball to be examined, with a manual instrument (an “Atti gauge”)manufactured by the Atti Engineering Company of Union City, N.J. Thismachine, equipped with a Federal Dial Gauge, Model D81-C, employs acalibrated spring under a known load. The sphere to be tested is forceda distance of 0.2 inch against this spring. If the spring, in turn,compresses 0.2 inch, the compression is rated at 100; if the springcompresses 0.1 inch, the compression value is rated as 0. Thus morecompressible, softer materials will have a lower Atti gauge values thanharder, less compressible materials. Compression measured with thisinstrument is also referred to as PGA compression. The center 11 may bea thermoset composition such as high cis or trans polybutadiene or maymay comprise a thermoset or thermoplastic metallocene (or other singlesite catalyzed polyolefin) such as a polybutadiene, polyethylenecopolymer, or EPR or EPDM. In the case of metallocenes, the polymer maybe cross-linked with a free radical source such as peroxide or byhigh-energy radiation. It is highly desirable that the center 11 be softand fast. The diameter of the center 11 is not critical but since a thinouter core layer(s) is desirable it should be greater than about 1.00inch and may be much higher, up to an outer diameter of about 1.62inches.

[0046] The enclosing two or more core layers of FIG. 1, may comprise thesame materials or even different compositions as disclosed above for thecenter 11, but at least one core layer must be significantly stiffer andharder than the center 11. At least one of the layers 12-14 has a ShoreC hardness of greater than 80 and preferably greater than 90 with a flexmodulus (per ASTM D-790) of greater than about 30,000 psi. Additionally,at least one core layer, 12-14, has a specific gravity of greater than1.25 g/cc, preferably greater than 1.50 g/cc and most preferably greaterthan 1.75 g/cc. This will increase the moment of inertia of the overallball, and subsequently lower spin rates when a driver golf club is used.This may be coupled with the use of unfilled or even foamed densityreducing material to reduce specific gravity of the center 11 and anyinner core laminate layers 12-13 to further increase the moment ofinertia of the ball. Each outer core layer 12-14 has a thickness of from0.001 to 0.100 inches and preferably from about 0.015 to 0.050 inches.Optionally, one or more layers 12-14 may serve as moisture barrierlayers that will protect against reduced COR values, due to moisturetake-up by the center 11. The use of moisture barriers is described inco-pending patent application Ser. No. 09/973,342, which is incorporatedby reference herein in its entirety. FIG. 1 further describes anembodiment of the invention wherein a single layer 14 serves one or moreof the functions described above, i.e. stiffness, high specific gravity,and moisture barrier. More specifically, one or more layers 12-14 havinga moisture vapor transmission rate that is less than that of the cover.

[0047] The cover 15 comprises one or more layers of a relatively softmaterial that supplies high partial spin to the ball when struck by awedge club. Preferably, the cover 15 comprises a single layer. The cover15 should have good durability as provided by cast polyurethane,polyurea, polyurethane ionomer, or a thermoplastic such as athermoplastic urethane, ionomer blend, fusabond, etc. It should have aShore D hardness or less than 65, preferably less than 60, andpreferably have a thickness of from about 0.010 to 0.055 inches, morepreferably from about 0.020 to 0.040 inches. While multi-layered coversmay be employed to fine tune spin and feel, the present invention doesnot require them to provide optimal performance.

[0048] In accordance with an embodiment of the present invention (hereinreferred to as example 1 as shown in FIG. 1), the center 11 has adiameter of 1.60 inches, a shore C hardness of 60, a compression of 50and a COR of 0.800. It also has a specific gravity of about 1.1 g/cc.Center 11 is enclosed by two core layers, an intermediate core layer 13and an outermost core layer 14. The outermost core layer 14 having aShore C hardness of 80 or greater, a thickness of 0.020 inches, and atungsten filler such that the core layer 14 will have a specific gravityof greater than 1.3 g/cc. The cover 15 is of a material such as castpolyurethane and having a hardness of less than 65 D and a thickness of0.020 inches. The overall ball 10 has a COR value of greater than 0.790,preferably greater than 0.800 and a compression of less than 100,preferably less than 90. The outermost core layer 14 can function as amoisture barrier. It has a moisture vapor transmission rate less thanthat of the cover layer and more preferably similar to the moisturevapor transmission rate of an ionomer resin such as Surlyn®, which is inthe range of about 0.45 to about 0.95 grams per mm/m² per day. Themoisture vapor transmission rate is defined as: the mass of moisturevapor that diffuses into a material of a given thickness per unit areaper unit time. The preferred standards of measuring the moisture vaportransmission rate include: ASTM F1249-90 entitled “Standard Test Methodfor Water Vapor Transmission Rate Through Plastic Film and SheetingUsing a Modulated Infrared Sensor,” and ASTM F372-99 entitled “StandardTest Method for Water Vapor Transmission Rate of Flexible BarrierMaterials Using an Infrared Detection Technique,” among others.

[0049] In another embodiment (herein referred to as example 2 as shownin FIG. 2), the center 11 is the same as in example 1 with the exceptionthat the size of its diameter is about 1.50 inches in stead of about1.60 inches. Center 11 is enclosed with four intermediate layers 17 a,17 b, 17 c, and 17 d, and a rigid outermost core layer 14. Any of thecore layers may function as a moisture barrier. The outermost core layer14 is generally rigid and has a Shore C hardness of 90 or greater, athickness of about 0.025 inches and a specific gravity of about 1.25g/cc, more preferably 1.50, and most preferably about 1.75 g/cc. Theoutermost core layer 14 has a thickness between about 0.001 inches toabout 0.1 inches. The cover 15 has a hardness of less than about 60 Dand a thickness between about 0.01 inches to about 0.55 inches. The flexmodulus of the center 11 is less than 20,000 psi and the flex moduluslevels of the intermediate layers 17 a, 17 b, 17 c, 17 d, and theoutermost core layer 14 progressively increases with the outermost corelayer being greater than 30,000 psi and preferably greater than 40,000psi. The core layers each are in a thickness range from about 0.001inches to about 0.10 inches. Whereas, there may be embodiments whereinthe rigid qualities of the outermost core 14 also appear in one of theinner intermediate layers 17 a, 17 b, or 17 c, the rigidity of theoutermost core 14 is necessary to the overall desired performance of theball 10.

[0050] The above two examples are an improvement over the golf ballconstructions of either U.S. patent application Ser. No. 09/948,692 orU.S. application Ser. No. 09/815,753. The manipulation of moment ofinertia via the filling (or foaming or otherwise reducing specificgravity) of the center 11 and inner laminate layers 12-14 provide theopportunity to further improve upon distance and spin. The low specificgravity center 11 or layers 12 or 13 can be made from a number ofsuitable materials, so long as the low specific gravity contributes tothe soft compression and resilience of the golf ball. The material canbe from a thermosetting syntactic foam with hollow sphere fillers ormicrospheres in a polymeric matrix of epoxy, urethane, polyester or anysuitable thermosetting binder, where the cured composition has aspecific gravity less than 1.1 g/cc and preferably less than 1.0 g/cc.Additionally, any number of foamed or otherwise specific gravity reducedthermoplastic or thermosetting polymer compositions may also be usedsuch as metallocene-catalyzed polymers and blends thereof described inU.S. Pat. Nos. 5,824,746 and 6,025,442 which are incorporated byreference herein in their entirety. Further, a thermoset polyurethanecomposition having a specific gravity or less than 1.0 g/cc such as anucleated reaction injection molded or cast polyurethane may be used.Such a composition may result in a gas-filled or cellular solid layer.

[0051] As discussed in U.S. Pat. No. 5,971,870, which is incorporated byreference herein in its entirety, fillers may be or are typically in afinely divided form. For example, in a size generally less than about 20mesh, preferably less than about 100 mesh U.S. standard size, except forfibers and flock, which are generally elongated, flock and fiber sizesshould be small enough to facilitate processing. Filler particle sizewill depend upon desired effect, cost, ease of addition, and dustingconsiderations. The filler preferably is selected from the groupconsisting of precipitated hydrated silica, clay, talc, asbestos, glassfibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zincsulfide, lithopone, silicates, silicon carbide, diatomaceous earth,polyvinyl chloride, carbonates, metals, metal alloys, tungsten carbide,metal oxides, metal stearates, particulate carbonaceous materials, microballoons, and combinations thereof. Non-limiting examples of suitablefillers, their densities, and their preferred uses are as follows:Filler Type Sp. Gr. Comments Precipitated hydrated silica 2.0 1, 2 Clay2.62 1, 2 Talc 2.85 1, 2 Asbestos 2.5 1, 2 Glass fibers 2.55 1, 2 Aramidfibers (KEVLAR ®) 1.44 1, 2 Mica 2.8 1, 2 Calcium metasilicate 2.9 1, 2Barium sulfate 4.6 1, 2 Zinc sulfide 4.1 1, 2 Lithopone 4.2-4.3 1, 2Silicates 2.1 1, 2 Silicon carbide patelets 3.18 1, 2 Silicon carbidewhiskers 3.2 1, 2 Tungsten carbide 15.6 1    Tungsten oxide 5.8 1   Diatomaceous earth 2.3 1, 2 Polyvinyl chloride 1.41 1, 2 CarbonatesCalcium carbonate 2.71 1, 2 Magnesium carbonate 2.20 1, 2 Metals andAlloys (powders) Titanium 4.51 1    Tungsten 19.35 1    Aluminum 2.701    Bismuth 9.78 1    Nickel 8.90 1    Molybdenum 10.2 1    Iron 7.861    Steel 7.8-7.9 1    Lead 11.4 1, 2 Copper 8.94 1    Brass 8.2-8.41    Boron 2.34 1    Boron carbide whiskers 2.52 1, 2 Bronze 8.70-8.741    Cobalt 8.92 1    Beryllium 1.84 1    Zinc 7.14 1    Tin 7.31 1   Metal Oxides Zinc oxide 5.57 1, 2 Iron oxide 5.1 1, 2 Aluminum oxide 4.0Titanium oxide 3.9-4.1 1, 2 Magnesium oxide 3.3-3.5 1, 2 Zirconium oxide5.73 1, 2 Metal Stearates Zinc stearate 1.09 3, 4 Calcium stearate 1.033, 4 Barium stearate 1.23 3, 4 Lithium stearate 1.01 3, 4 Magnesiumstearate 1.03 3, 4 Particulate carbonaceous materials Graphite 1.5-1.81, 2 Carbon black 1.8 1, 2 Natural bitumen 1.2-1.4 1, 2 Cotton flock1.3-1.4 1, 2 Cellulose flock 1.15-1.5  1, 2 Leather fiber 1.2-1.4 1, 2Micro balloons Glass 0.15-1.1  1, 2 Ceramic 0.2-0.7 1, 2 Fly ash 0.6-0.81, 2 Coupling Agents Adhesion Promoters Titanates 0.95-1.11 Zirconates0.92-1.11 Silane 0.95-1.2 

[0052] The increased hardness of the intermediate core layer 13 inreference to the innermost core layer 12 and the outermost core layer 14provides the ball 10 with performance characteristics that have beenassociated primarily with dual cover layer golf balls using ionomerinner cover layers.

[0053] Examining a golf ball made with a small center of 1 inch or lessand relatively thick core layers, each having a thickness of greaterthan 0.1 inch, it will be seen that this structure decreases ballinitial velocity and reduces the ball spin rate effects. When impactinga golf ball with different clubs within a set, the impact speed and theimpact angle are changed. On an average, for a tour professional theimpact speed of a driver is about 110 miles an hour. The averageprofessional hitting a 5 iron will have an impact speed of about 90miles an hour and the wedge impact velocity is less than about 80 milesan hour. Moreover, the force on the golf ball is broken up into twocomponents, the normal force that is normal to the club face and thetangential force that is parallel to the club face. Since mostprofessionals use a driver having a loft of about 10 degrees, thetangential force is significantly less than the normal force. However,when using a wedge having a loft between 48 and 60 degrees, thetangential force becomes very significant. For example, experimentaldata shows that with a clubhead having an impact velocity of about 95miles an hour and an angle of 20 degrees, a two piece ball has a maximumdeflection of about 0.151 inches. When hit with a club head at 95 milesan hour and an impact angle of 40 degrees, the ball has a maximumdeflection of about 0.128 inches or a difference of 0.023 inches. Thus,the impact deflection depends significantly on the impact angle, and byhaving outer layers of less than 0.1 inch, the spin characteristics ofthe ball is altered for different clubs within a set as discussed inmore detail below. Golf balls can be made for all types of golfers, byproperly utilizing the hardness and density of the center, core layersand cover material. By creating a golf ball core with relatively thinouter layers that progressively get harder, the spin rate of the ball issurprisingly good for a player that desires a high spin rate golf ball.More particularly, when this type of player hits the ball with a shortiron, only the outer layer and cover affect the spin rate of the ball.By incorporating a very hard core outer layer and a soft cover, the spinrate is maximized for the short iron shot such as a wedge having anangle of about 48 to 60 degrees. In order to reduce the spin rate alittle for middle iron shots such as a 6 iron having a oft of about 32degrees to make sure that sufficient distance is obtained, the secondlayer is softer than the third layer. Similarly, to decrease the spinrate, provide good distance and a good trajectory for long irons such sa 3 iron having a loft of about 20 degrees, the first layer is softerthan the second layer. Finally, for a low spin rate with the driverhaving a loft of about 8 to 12 degrees, the center is made very soft.

[0054] Table 1 sets forth the contents that can make-up the golf ballcore in the first embodiment. The compositions used to prepare the golfball core of this embodiment are all in parts per hundred (pph), basedon 100 parts of polybutadiene. The fillers used in the compositions ofthese examples are regrind and barium sulfate (BaSO¼). Vulcup 40KE™. andVarox 231XL™, are free radical initiators, and are a-a bis(t-butylperoxy) diisopropylbenzene and 1,1-di(t-butylperoxy)3,3,5-trimethyl cyclohexane, respectively. TABLE CORE COMPOSITIONS (pph)Layer No. Center 1 2 3 Polybutadiene 100 100 100 100 Polywate 325 26 2318 13 Vulcup 40KE ™ 0.3 .3 .3 .3 Varox 231XL ™ 0.6 .5 .5 .5 BaSO.sub.431 26 25 25 Zinc Diacrylate 30 32 35 47 SR-350 2 2 2 6 Calcium Oxide 3 00 0 Zinc Oxide 0 3 6 6

[0055] All the ingredients except the peroxides were mixed in a ProcessLab Brabender mixer to about 180-200.degree. F. Peroxides were added inthe second stage to the initial mixture, and the resulting mixture wasremoved from the Brabender and blended on a lab mill to insurehomogeneity. After mixing, the mixture was then hand rolled using alaboratory mill and cut into pieces or “preps”. To make the core centers11 the preps were then compression molded at about 160° C. for about 15minutes. To fabricate the outer layers, polybutadiene rubber materialwas rolled into flat sheets and the sheets were stacked to form alaminate. The laminate was then compression molded around the centers asdescribed above. To form the finished golf balls, the cores were groundand inserted into two cover hemispheres of materials that were suitablefor use in a cover layer. These may include any number of partially orfully neutralized ionomers such as those disclosed in the parentapplication, or described in WO 00/23519, WO 01/29129. Also anythermosetting or thermoplastic polyurethanes or polyureas, including anyaliphatic or aromatic polyether or polyester polyurethanes such as butnot limited to those disclosed in U.S. Pat. Nos. 6,309,313; 6,210,294;6,117,024; 5,908,358; 5,929,189; 5,334,673 and U.S. application Ser. No.09/466,434. Additionally, other suitable cover materials are disclosedin U.S. Pat. No. 5,919,100 and also in any of the co-pendingapplications referenced herein.

[0056] Referring back to the core layers 12, 13 and 14, these can bemade of thermosetting or thermoplastic materials. For example, thefirst, second and third layers 12, 13 and 14 can be formed fromthermoplastic elastomers, functionalized styrene-butadiene elastomers,thermoplastic rubbers, thermoset elastomers, thermoplastic urethanes,metallocene polymers, urethanes, or ionomer resins, or blends thereof.

[0057] The thermoplastic elastomers include dynamically vulcanizedthermoplastic elastomers and blends thereof. Suitable dynamicallyvulcanized thermoplastic elastomers include Santoprene®., Sarlink®,Vyram®, Dytron® and Vistaflex®. Santoprene® is the trademark for adynamically vulcanized PP/EPDM. Santoprene® 203-40 is an example of apreferred Santoprene® and is commercially available from AdvancedElastomer Systems.

[0058] Examples of suitable functionalized styrene-butadiene elastomersinclude Kraton FG-1901x and FG-1921x, available from the ShellCorporation. Examples of suitable thermoplastic polyurethanes includeEstane® 58133, Estane® 58134 and Estane® 58144, which are available fromthe B.F. Goodrich Company. Further, the materials for the first, secondand third layers 12, 13 and 14 described above may be in the form of afoamed polymeric material. For example, suitable metallocene polymersinclude foams of thermoplastic elastomers based on metallocenesingle-site catalyst-based foams. Such metallocene-based foams arecommercially available from Sentinel Products of Hyannis, Mass.

[0059] Suitable thermoplastic polyetheresters include Hytrel® 3078,Hytrel® G3548W, and Hytrel® G4078W which are commercially available fromDuPont. Suitable thermoplastic polyetheramides include Pebax® 2533,Pebax® 3533, Pebax® 1205 and Pebax® 4033 which are available fromElf-Atochem. Suitable thermoplastic polyesters include polybutyleneterephthalate.

[0060] Suitable thermoplastic ionomer resins are obtained by providing across metallic bond to polymers of monoolefin with at least one memberselected from the group consisting of unsaturated mono- or di-carboxylicacids having 3 to 12 carbon atoms and esters thereof. The polymercontains 1 to 50% by weight of the unsaturated mono- or di-carboxylicacid and/or ester thereof. More particularly,low modulus ionomers, suchas acid-containing ethylene copolymer ionomers, include E/X/Y copolymerswhere E is ethylene, X is a softening comonomer such as acrylate ormethacrylate present in 0-50 (preferably 0-25, most preferably 0-2),weight percent of the polymer, and Y is acrylic or methacrylic acidpresent in 5-35 (preferably 10-35, most preferably 15-35, making theionomer a high acid ionomer) weight percent of the polymer, wherein theacid moiety is neutralized 1-100% (preferably at least 40%, mostpreferably at least about 60%) to form an ionomer by a cation such aslithium*, sodium*, potassium, magnesium*, calcium, barium, lead, tin,zinc* or aluminum (*=preferred), or a combination of such cations.Specific acid-containing ethylene copolymers include ethylene/acrylicacid, ethylene/methacrylic acid, ethylene/acrylic acid/n-butyl acrylate,ethylene/methacrylic acid/n-butyl acrylate, ethylene/methacrylicacid/methyl acrylate, ethylene/methacrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl methacrylate, and ethylene/acrylicacid/n-butyl methacrylate. Preferred acid-containing ethylene copolymersinclude ethylene/methacrylic acid, ethylene/acrylic acid,ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate andethylene/acrylic acid/methyl acrylate copolymers. The most preferredacid-containing ethylene copolymers are ethylene/methacrylic acid,ethylene/acrylic acid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

[0061] Such ionomer resins include SURLYN®. and lotek®, which arecommercially available from DuPont and Exxon, respectively. Likewise,other conventional materials such as balata, elastomer and polyethylenemay also be used in the first, second and third layers 12, 13 and 14 ofthe present invention.

[0062] Such thermoplastic blends comprise about 1% to about 99% byweight of a first thermoplastic and about 99% to about 1% by weight of asecond thermoplastic.

[0063] Preferably the thermoplastic blend comprises about 5% to about95% by weight of a first thermoplastic and about 5% to about 95% byweight of a second thermoplastic. In a preferred embodiment of thepresent invention, the first thermoplastic material of the blend is adynamically vulcanized thermoplastic elastomer, such as Santoprene®.

[0064] The properties such as hardness, Bayshore resilience modulus,center diameter and layer thickness of the golf balls of the presentinvention have been found to affect play characteristics such as spin,initial velocity and feel of golf balls.

[0065] The golf ball of the present invention can have an overalldiameter of any size. Although the United States Golf Association (USGA)specifications limit the minimum size of a competition golf ball to morethan 1.680 inches in diameter, there is no specification as to themaximum diameter. Moreover, golf balls of any size can be used forrecreational play. The preferred diameter of the present golf balls isfrom about 1.680 inches to about 1.800 inches. The more preferreddiameter is from about 1.680 inches to about 1.760 inches. The mostpreferred diameter is about 1.680 inches to about 1.740 inches.

[0066] While it is apparent that the illustrative embodiments of theinvention herein disclosed fulfill the objectives stated above, it willbe appreciated that numerous modifications and other embodiments may bedevised by those skilled in the art. Therefore, it will be understoodthat the appended claims are intended to cover all such modificationsand embodiments which come within the spirit and scope of the presentinvention.

What is claimed is:
 1. A golf ball comprising: a multi-layer corehaving: a center having a Shore C surface hardness of less than about 80and a compression of less than 70, at least one rigid outer core layerhaving a flex modulus greater than 40,000 psi and a Shore C hardness ofgreater than 80; an intermediate core layer, interposed between thecenter and the rigid outer core layer, having a flex modulus less than20,000 psi and a Shore C hardness less than 60; and a cover having aShore D hardness of less than
 65. 2. The golf ball according to claim 1,wherein the center has a compression of less than
 50. 3. The golf ballaccording to claim 1, wherein the center has a Shore C hardness of lessthan
 60. 4. The golf ball according to claim 1, wherein at least onerigid outer core layer has a Shore C hardness of greater than
 90. 5. Thegolf ball according to claim 1, wherein the cover has a Shore D hardnessof less than
 60. 6. The golf ball according to claim 1, wherein themulti-layer core has a diameter greater than 1.55 inches.
 7. The golfball according to claim 1, wherein each core layer has a thickness fromabout 0.015 to 0.05 inches.
 8. The golf ball according to claim 1,wherein the center comprises a polybutadiene rubber and at least onecore layer comprises either a thermoset composition such as high cis ortrans polybutadiene or a thermoset metallocene or thermoplasticmetallocene such as a polybutadiene or polyethylene copolymer.
 9. Thegolf ball according to claim 1, wherein the cover layer is selected fromthe group consisting of a cast polyurethane, polyurea,polyurethane-ionomer, thermoplastic polyurethane, polyamide, polyester,a single-site catalyzed polymer or a partially neutralized ionomer orfully neutralized ionomer.
 10. The golf ball according to claim 1,wherein the cover has a thickness of between 0.01 to 0.055 inches. 11.The golf ball according to claim 1, wherein the center has a specificgravity of less than 1.1 g/cc.
 12. The golf ball according to claim 11,wherein at least one of the core layers has a specific gravity ofgreater than 1.25 g/cc.
 13. The golf ball according to claim 11, whereinat least one of the core layers has a specific gravity of greater than1.5 g/cc.
 14. The golf ball according to claim 11, wherein at least oneof the core layers has a specific gravity of greater than 1.75 g/cc. 15.The golf ball according to claim 1, wherein at least one of the corelayers has a moisture vapor transmission rate that is lower than that ofthe cover.
 16. A golf ball having a multi-layer core, the corecomprising: a center having a Shore C surface hardness of less thanabout 60, a compression of less than about 70, and a flex modulus lessthan about 20,000 psi; a plurality of core layers progressively disposedabout and away from the center, including a first core layer coveringthe center, the first core layer having a flex modulus greater than theflex modulus of the center, and each progressive core layer having agreater flex modulus than the core layer beneath it; and a cover havinga Shore D hardness of less than
 60. 17. The golf ball according to claim16, wherein each core layer has a thickness from about 0.001 inches toabout 0.10 inches.
 18. The golf ball according to claim 16, wherein thecover has a thickness of between 0.01 to 0.055 inches.
 19. The golf ballaccording to claim 16, wherein the center comprises a polybutadienerubber and at least one core layer comprises either a thermosetcomposition such as high cis or trans polybutadiene or a thermosetmetallocene or thermoplastic metallocene such as a polybutadiene orpolyethylene copolymer.
 20. The golf ball according to claim 16, whereinthe cover layer is selected from the group consisting of a castpolyurethane, polyurea, polyurethane-ionomer, thermoplasticpolyurethane, polyamide, polyester, a single-site catalyzed polymer, ora partially filled neutralized ionomer.
 21. A golf ball having amulti-layer core, the core comprising: a center having a Shore C surfacehardness of less than about 60, a compression of less than about 70, anda flex modulus less than about 20,000 psi; a plurality of core layersprogressively disposed about and away from the center, including a firstcore layer disposed about the center and having a flex modulus no lessthan the flex modulus of the center, and each progressive core layerhaving a flex modulus no less than the flex modulus of the core layerbeneath it; and a cover having a Shore D hardness of less than
 60. 22.The golf ball according to claim 21, wherein the cover comprises asingle layer having a thickness of about 0.010 inches to about 0.055inches.
 23. The golf ball according to claim 21, wherein each core layerhas a thickness from about 0.001 inches to about 0.10 inches.
 24. Thegolf ball according to claim 21, wherein the center comprises apolybutadiene rubber and at least one core layer comprises either athermoset composition such as high cis or trans polybutadiene or athermoset metallocene or thermoplastic metallocene such as apolybutadiene or polyethylene copolymer.
 25. The golf ball according toclaim 21, wherein the cover layer is selected from the group consistingof a cast polyurethane, polyurea, polyurethane-ionomer, thermoplasticpolyurethane, polyamide, polyester, a single-site catalyzed polymer, ora partially filled neutralized ionomer.